“Blueberries indicator” experiment
How to make pH indicator from blueberries
You’ve all heard of the indicators phenolphthalein, litmus and methyl-orange, but unless you’re a chemist, they’re not easy to obtain. But there’s a worthy alternative to them – juicy blueberries! In this experiment you’ll learn how to extract coloring agents from blueberries, and use them to determine the acidity of solutions.
Observe safety measures when working with heating devices and hot liquids.
Reagents and equipment:
- blueberries (200 g);
- hot water (150 ml);
- 9% table vinegar (100 ml);
- lemon juice (100 ml);
- fizzy water (carbonic acid solution, 100 ml);
- water (100 ml);
- 2% baking soda solution (100 ml);
- pipe-cleaning liquid (10% sodium hydroxide solution, 100 ml);
- 15 glasses;
- glass container;
- cotton wool.
In a glass container, crush blueberries and pour hot water over them. Filter the resulting mixture through a funnel with cotton wool. Using a pipette, drip several drops of filtrate into the glasses and gradually fill with the following solutions: lemon juice, acetic acid, fizzy water, plain water, baking soda solution and pipe-cleaning liquid. Watch the indicator change color from red to yellow through blue.
The potential of hydrogen (acidity) of pH is a measurement of the activity of hydrogen solutions in a solution. If pH>7, the medium is alkaline, if pH<7, it is acidic. If pH=7, the medium is neutral. Household cleaning agents with a strong acidic or alkaline pH may be harmful to the body. The indicator does not make a substance less dangerous and does not provide protection from it – it simply warns of danger.
The ”causticity” of substances can be determine in the home using a blueberry indicator. Blueberries contain coloring agents – anthocyanins. Depending on the acidity of alkalinity of the medium, anthocyanins turn different colors. In a strong acidic medium (lemon juice, vinegar) they turn red, in a weak acidic and neutral medium they turn purple, in a weak alkaline medium they turn blue, and in a strong alkaline medium they turn yellow.